This invention relates to an exercise device, and more particularly to a magnetic resistance arrangement for an exercise device.
An exercise device, such as a stationary bicycle trainer, incorporates a resistance unit for applying resistance during operation of the device. The resistance unit typically includes a rotatable member, such as a shaft or roller, that rotates in response to work performed by the user. Resistance to rotation of the shaft or roller is accomplished several different ways, including wind resistance, fluid resistance, and resistance established by one or more magnetic members that interact with an electrically conductive member which rotates along with the shaft or roller, to establish eddy current resistance to rotation of the shaft or roller. Examples of magnetic resistance mechanisms are shown and described in Wei. et. al. U.S. Pat. No. 5,879,273 as well as copending U.S. patent application Ser. No. 10/054,781 filed Jan. 23, 2002, the disclosures of which are hereby incorporated by reference. The '781 patent application discloses a magnetic resistance arrangement in which one or more magnets are located adjacent a rotating electrically conductive member. The magnets are moved outwardly under the influence of centrifugal forces resulting from rotation of the rotatable member to which the magnets are mounted. Such outward movement of the magnets increases the distance of the magnets from the axis of rotation of the rotatable shaft or roller, to increase the resistance to rotation of the shaft or roller in proportion to increased speed of operation. The '273 patent discloses a system in which one or more magnets are mounted to a plate. The plate is interconnected with an adjustment mechanism by which the spacing between the magnets and the rotatable electrically conductive member can be adjusted, to vary the eddy current force that applies resistance during operation of the device.
It is an object of the present invention to provide an adjustable magnetic resistance arrangement for a resistance unit for use in an exercise device such as a bicycle trainer. It is a further object of the invention to provide such an adjustable magnetic resistance arrangement in which the resistance is adjusted by the user independent of the speed of operation of the device. It is a further object of the invention to provide such an adjustable magnetic resistance arrangement which involves a relatively small number of parts, to facilitate assembly and to provide a relatively low cost of manufacture. Yet another object of the invention is to provide such an adjustable magnetic resistance arrangement in which resistance is adjusted by varying the space between a magnetic member and a rotatable electrically conductive member interconnected with a rotatable shaft or roller forming a part of the exercise device.
In accordance with the present invention, a resistance unit, such as for use in an exercise device, includes a body or housing and a rotatable member, such as a shaft or roller, that is rotatably mounted to the body or housing. In one application, the exercise device may be in the form of a stationary bicycle trainer in which the driven wheel of a bicycle is engaged with the shaft or roller, to impart rotation to the shaft or roller.
An electrically conductive member, such as a plate, is interconnected with the rotatable member. In one embodiment, the rotatable member is interconnected with a flywheel that rotates along with the rotatable member, and the electrically conductive member is secured to the flywheel so as to rotate along with the rotatable member and the flywheel. A magnetic member is mounted to the housing, and interacts with the electrically conductive member to establish eddy current resistance to rotation of the electrically conductive member, which is transferred to the rotatable member through the flywheel.
An adjustment mechanism is interposed between the magnetic member and the body or housing, for adjusting the space between the magnetic member and the electrically conductive member to vary the strength of the eddy current resistance. In one embodiment, the magnetic member is received within a passage formed in the body or housing, and the adjustment mechanism is operable to vary the position of the magnetic member within the passage so as to move the magnetic member toward and away from the electrically conductive member. The body or housing may define a pair of oppositely facing surfaces between which the passage is located. The electrically conductive member is located adjacent one of the oppositely facing surfaces, and the adjustment mechanism includes an actuator that is located adjacent the other of the oppositely facing surfaces. The actuator is preferably rotatable, and the adjustment mechanism is configured so as to vary the position of the magnetic member in response to rotation of the actuator.
A vane arrangement may be interposed between the electrically conductive member and the flywheel, for providing air movement upon rotation of the rotatable member and the flywheel, to cool bearings that provide rotatable mounting of the rotatable member to the body or housing.
The invention contemplates a resistance unit as summarized above, as well as an improvement in a resistance unit and a method of adjusting the resistance of a resistance unit, substantially in accordance with the foregoing summary.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.